Three-dimensional Finite Element Model Research Articles

Field Investigation and Numerical Modeling for the Seismic Assessment of the Castle of Lanjarón, Spain

The Castle of Lanjarón is a 16th century stronghold located in Andalucía, Spain. After losing its military function, the castle was abandoned, leading to significant decay. Designated a national heritage site in 1985, recent efforts have sought to preserve its historical and cultural value. This study outlines an inspection and diagnosis campaign carried out on the castle. Non-destructive tests (NDTs) were employed to characterize the properties of the masonry, using both mechanical and wave-based methods. Dynamic identification was performed to determine dynamic and modal properties of the structure, which were used to develop and calibrate a three-dimensional (3D) finite element model (FEM) of the west wall, based on homogenized masonry material. Limit analysis and non-linear static (pushover) analysis under various boundary conditions were conducted to determine the maximum relative load factor in the out-of-plane direction. The results were compared to the expected peak ground acceleration (PGA) of the area, showing that the maximum load capacity of the wall exceeds local seismic demands with a safety factor of 1.39. The study highlights the efficacy of pairing a homogenized macro-modeling approach with wave-based and dynamic identification methods, particularly for resource efficiency. Finally, recommendations for future conservation efforts have been provided.

Performance and robustness assessment of roadway masonry arch bridges to scour-induced damage using multiple traffic load models

Masonry arch bridges are highly vulnerable to floods and particularly to scour, as demonstrated by the many collapses that regularly occur in Europe. Scour levels that do not directly cause the collapse of a bridge may result in a significant reduction of their capability to withstand traffic loading. Thus, research on the performance of masonry arch bridges under combined scour and traffic loading, and their structural robustness, is of paramount importance.This study evaluates the behaviour of masonry arch bridges subjected to scour and traffic loading by analysing a representative case study with a three-dimensional finite element model developed in Abaqus according to a macro-modelling approach. Traffic load is selected in accordance with different code-based models, including those provided by Italian guidelines for safety assessment of existing bridges. The scouring process is imposed through the progressive removal of elements at the foundation level. Displacements and internal stress distributions for different bridge components are recorded and the capacity of the masonry bridge is estimated under increasing traffic load for different scour levels. Results are obtained in terms of both local and global response parameters to provide useful information on threshold levels for bridge safety and monitoring. The sensitivity of the bridge structural performance to material properties and traffic load position is also assessed. The study results can be useful to inform the decisions to be taken by bridge stakeholders (e.g. close bridge, limit traffic, keep bridge open) based on scour and/or structural response measurements.

Biomechanical analysis of scoliosis correction under the influence of muscular and external forces.

(1) Background: External force orthopedics and the strengthening of paraspinal muscles through exercise are common orthopedic methods for adolescent scoliosis, yet the synergetic mechanism of the two in orthopedic correction remains unclear. (2) Methods: A three-dimensional finite element model of the scoliotic spine was established to accurately simulate the mechanical properties of tissues such as the spine, intervertebral discs, and ribs. By applying external forces in different directions to the scoliosis model, the orthopedic effects of these forces on scoliosis were analyzed. Furthermore, considering the influence of muscular forces on scoliosis, the role of muscle contraction in the correction of scoliosis was simulated. (3) Results: The applied external forces significantly reduced both the Cobb angle and the vertebral rotation angle of the scoliotic spine. Specifically, the Cobb angle was corrected from 25° to 14°, achieving a scoliosis correction rate of 44%, while the apical vertebral rotation angle was corrected from 10.8° to 8.59°, resulting in a rotation correction rate of 20.46%. Furthermore, with the addition of muscular forces, the scoliosis correction rate increased further to 75.08%, and the apical vertebral rotation correction rate reached 11.39%; (4) Conclusions: Simultaneous exercise of paraspinal muscles while wearing an orthosis to improve muscular imbalance, can further reduce the Cobb angle and enhance the orthopedic effect.

Assessing the Effectiveness of Dowel Bars in Jointed Plain Concrete Pavements Using Finite Element Modelling

Aggregate interlocking and dowel bar systems are the two primary mechanisms in a jointed plain concrete pavement for transferring the wheel loads from the loaded slab to the adjacent unloaded slab, avoiding critical stresses and excessive deformations across the joint. Aggregate interlocking is suitable for small joint openings, while the dowel bar provides effective load transmission for both smaller and wider joint openings. In this study, a three-dimensional finite element model was developed to investigate the structural performance of dowelled jointed plain concrete pavements. The developed model was compared with an analytical solution, i.e., Westergaard’s method. The current study investigated the effectiveness of the dowel bars in jointed plain concrete pavements considering the modulus of elasticity and the thickness of the base layer, as well as dowel bar diameter and length. Furthermore, the load transfer efficiency (LTE) of a rounded dowel bar was compared with that of plate dowel bars (i.e., rectangular and diamond-shaped dowel bars) of a similar cross-sectional area and length. This study showed that the LTE was enhanced by 4% when the base layer’s modulus of elasticity increased from 450 MPa to 6000 MPa, while the increase in stress was 23%. A 1.2% improvement in the LTE and a 2.1% reduction in flexural stress were observed as the base layer’s thickness increased from 100 to 250 mm. Moreover, increasing the dowel bar’s diameter from 20 mm to 38 mm enhanced the LTE by 4.3% and 3.8% for base layer moduli of 450 MPa and 4000 MPa, respectively. The corresponding rise in stresses was 10% and 5%. The diamond-shaped dowel bar of a 50 × 32 mm size showed a 0.48% increase in the LTE, while sizes of 100 × 16 mm and 200 × 8 mm reduced the stress 6.7% and 23.1%, respectively, compared to that in the rounded dowel bar. With rectangular dowel bars, a 4% rise in the stress was noted compared to that with the rounded dowel bar. Increasing the length of the diamond-shaped dowel bar slightly improved the LTE but had no impact on the stress in the concrete slab. The findings from this study can help highway engineers improve pavements’ durability, make cost-effective decisions, contribute to resource savings in large-scale concrete pavement projects, and enhance the overall quality of infrastructure.

Layerwise generalized formulation solved via a boundary discontinuous method for multilayered structures. Part 1: Plates

Abstract This article presents for the very first time a layerwise bending analytical solution for cross-ply laminated composite plates with clamped boundary conditions at all edges. The displacement field is implemented within the framework of the Carrera unified formulation at a layer level by employing Legendre polynomials. The governing equations are obtained by using the principle of virtual displacements statement. This work utilizes the boundary-discontinuous double Fourier series to provide analytical solutions. The high accuracy of the proposed solution is demonstrated by comparing the results with three-dimensional finite-element model (FEM) solutions of multilayered and sandwich plates for various side-to-thickness ratios. In conclusion, the highly accurate proposed solution might be used as a benchmark problem for new analytical or FEMs.

Stress State and Fatigue Life Assessment of the Bolts at the Outlet End of Fracturing Pump

The fracturing pump serves as a critical piece of equipment in enhancing oil and gas recovery rates. However, under the coupled action of high-pressure fluid pulsation circulation in the pump body and the vibration of fracturing equipment, the bolts connecting the fracturing pump and fracturing manifold flange are prone to fatigue failure. In this paper, a three-dimensional finite-element model of the threaded bolt connection structure at the fracturing pump outlet end with a fine thread structure was established, and the measured vibrational displacement of the fracturing pump under different driven modes was used as the load to obtain the internal stress state of the full-thread bolt and the double-headed bolt used in the fracturing operation site. Based on the stress state, the fatigue life of the two types of bolts under various loading conditions was then simulated using the Brown—Miller fatigue damage criterion. The results indicate that for bolts of the same structural type, the maximum stress and stress variation amplitude increase in the sequence of the diesel-driven, single-motor-driven, and dual-motor-driven methods. Additionally, under the same load, the stress of the full-thread bolt is lower than that of double-headed bolt. The fatigue life analysis results show that under the vibrational load of diesel drive, the full-thread bolt can obtain a longer fatigue life of approximately 2042.89 h. However, under the load of dual-motor-driven method, the fatigue life of double-headed bolt is the lowest, only 717.46 h. A comparison with the fatigue life of bolts in actual engineering projects indicates that the predicted fatigue life of the bolts is consistent with the actual service life, which can provide effective guidance for the inspection and maintenance of fracturing pump equipment.

Data-Driven Depiction of Aging Related Physiological Volume Shrinkage in Brain White Matter: An Image Processing Based Three-Dimensional Micromechanical Model

Abstract Aging in the human brain, both in healthy and pathological conditions, leads to significant microstructural alterations, resulting in cognitive decline, with cerebral atrophy being a major contributing factor. This atrophy, characterized by the loss of neurons and glial cells, plays a crucial role in the reduction of brain function. While magnetic resonance imaging (MRI) and magnetic resonance elastography (MRE) provide noninvasive tools to measure brain morphology (volume changes) and regional mechanical properties (tissue stiffness) at the millimeter scale, they are unable to capture cellular-level or micron-scale changes in brain tissue. The challenge is in correlating the mechanical property changes observed at the millimeter scale with the underlying cellular-level micro-architectural alterations. To address this limitation, an ensemble of three-dimensional micromechanical finite element (FE) models was developed, utilizing MRI/MRE data to compute the mechanics of the aging brain with a higher level of detail. Using image processing techniques in Python's NIBABEL library, a mathematical model was constructed to quantify volume fraction (VF) shrinkage in brain white matter (BWM). These models incorporate uniaxial tensile loading and simulate the interactions between axons, myelin, and the glial matrix. Among the three finite element models compared, model type III, which includes both volume fraction changes and shear modulus degeneration, showed a high-order age-related atrophy and brain softening. This approach emphasizes the significant role of computational mechanics in linking macroscopic MRI measurements to cellular-scale changes, enhancing our understanding of brain tissue degeneration.

Analysis of tire contact stresses and asphalt pavement rutting under gradient temperature and typical driving conditions

Studies on triaxial contact stresses and asphalt pavement rutting are of great significance for traffic safety and the durability of the asphalt pavement. Our new approach considers more evaluating indicators by investigating compressive creep, vertical, and longitudinal permanent deformation to analyse asphalt pavement rutting under triaxial contact stress during typical driving conditions. For this purpose, firstly sophisticated three-dimensional finite element models encompassing the truck-bus tire and asphalt pavement temperature are developed. Secondly, a comparative analysis was conducted by collating the predicted deformations obtained through finite element analysis with the deformations measured in laboratory experiments using specialized sensors. Finally, the rutting analysis process under triaxial contact stresses during typical driving conditions is established. The results show asphalt pavement exhibits different temperature gradient changes between daytime and nighttime during the summer season. The longitudinal contact stress under braking condition has a significant impact on the longitudinal permanent deformation and compressive creep of asphalt pavement, especially, the longitudinal permanent deformation of the feature points in the middle layer exhibits the most pronounced sensitivity to this contact stress. In addition, the maximal compressive creep is observed at the top of the middle layer, although the characteristic positions for the maximum values of positive and negative creep differ. The proposed new method is beneficial for improving the accuracy and comprehensiveness of asphalt pavement rutting analysis.

The Effect of BEOL Design Factors on the Thermal Reliability of Flip-Chip Chip-Scale Packaging

With the development of high-density integrated chips, low-k dielectric materials are used in the back end of line (BEOL) to reduce signal delay. However, due to the application of fine-pitch packages with high-hardness copper pillars, BEOL is susceptible to chip package interaction (CPI), which leads to reliability issues such as the delamination of interlayer dielectric (ILD) layers. In order to improve package reliability, the effect of CPI at multi-scale needs to be explored in terms of package integration. In this paper, the stress of BEOL in the flip-chip chip-scale packaging (FCCSP) model during thermal cycling is investigated by using the finite-element-based sub-model approach. A three-dimensional (3D) multi-level finite element model is established based on the FCCSP. The wiring layers were treated by the equivalent homogenization method to ensure high prediction accuracy. The stress distribution of the BEOL around the critical bump was analyzed. The cracking risk of the interface layer of the BEOL was assessed by pre-cracking at a dangerous location. In addition, the effects of the epoxy molding compound (EMC) thickness, polyimide (PI) opening, and coefficient of thermal expansion (CTE) of the underfill on cracking were investigated. The simulation results show that the first principal stress of BEOL is higher at high-temperature moments than at low-temperature moments, and mainly concentrated near the PI opening. Compared with the oxide layer, the low-k layer has a higher risk of cracking. A smaller EMC thickness, lower CTE of the underfill, and larger PI opening help to reduce the risk of cracking in the BEOL.

Impacts of surface wear of attachments on maxillary canine distalization with clear aligners: a three-dimensional finite element study.

This study established three-dimensional finite element models to explore the impacts of surface wear of attachments on maxillary canine distalization with clear aligners, thereby guiding the clinical application of attachments and enhancing the efficiency of clear aligner therapy. Finite element models of maxillary canine distalization, including the maxilla, dentition, periodontal ligament, attachments (in both initial and worn states), and clear aligners, were established. Two groups of attachments (vertical rectangular attachment and optimized root control attachment) and five working conditions representing different degrees of attachment wear (M0, M2, M4, M6, and M8) were designed for canine distalization. Tooth displacement and equivalent stress in the roots and periodontal ligaments were analyzed. The canines in both groups exhibited a tipping movement pattern under all working conditions. By M8, the distal displacement of the canine crown, the equivalent stress values in the roots, and the equivalent stress values in the periodontal ligaments in the rectangular attachment group decreased by 12.04%, 30.80%, and 16.48%, respectively, compared to M0. In the optimized root control attachment group, these values decreased by 24.98%, 34.69%, and 19.15%, respectively. However, under all working conditions, the canines in the rectangular attachment group presented greater displacement and stress. The greatest reduction in canine crown distal displacement and stress values was observed between M6 and M8 in the rectangular attachment group, but the efficiency of canine distalization was still 64.30% at M8, with minimal change. In the optimized root control attachment group, the greatest reduction was observed in M4-M6, and the efficiency of canine distalization decreased to less than 60% in response to M6. The canines tended to tip when maxillary canine distalization was performed with clear aligners. Attachment wear led to a reduction in the efficiency of canine distalization. Compared with optimized root control attachments, the impact was less significant for rectangular attachments. Once optimized root control attachments have been in place for more than 4 months and maxillary canine distalization is still required, orthodontists should closely monitor the wear of these attachments. If necessary, timely restoration or rebonding of the attachments is recommended.

Multi-field modelling and temperature rise analysis for the pantograph-catenary contact of metro train during a temporary stop

Metro trains are a type of electrical multiple unit (EMU) that obtain energy through electrical contact between the pantograph strip and the contact wire. When a metro train arrives at a station or temporarily halts on the track, the catenary system must maintain the supply of electrical current to support for essential functions such as air conditioning, illumination, door operation, braking, startup, and other onboard devices. However, due to the presence of contact resistance, concentrated Joule heating is generated the interface of the pantograph-catenary system when electrical current flows through it. This static contact condition can lead to overheating, which may result in thermal damage to the pantograph strip and potentially cause wire breakage accidents. Therefore, investigating the temperature rise at the pantograph-catenary contact when the train halts is crucial. The characteristics of the contact force, contact resistance, and thermal conductivity within the pantograph-catenary system indicate that this contact represents a complex interaction involving thermal, mechanical, and electrical behaviors. Consequently, a multi-field coupled model is required. In this study, a three-dimensional finite element model that incorporates the thermal-mechanical-electrical interactions of the pantograph-catenary contact is proposed. Based on this model, simulations of the temperature rise during static contact between the pantograph strip and the contact wire is simulated to examine, examining the effects of contact force, contact resistance, thermal conductivity, and the wear condition of the contact wire. The model and analytical results presented in this paper provide valuable insights for the parameter design and optimization of the pantograph-catenary system.

A numerical study on the seismic retrofit of Haitian reinforced concrete building frames

Many countries with moderate and high seismic risk have upgraded their building design standards and have developed techniques to strengthen their seismically deficient buildings. However, very limited research has been conducted on the seismic evaluation and retrofit of Haiti’s existing buildings. In an effort toward filling this gap, after reviewing the reinforced concrete (RC) building construction practices in Haiti, this article numerically evaluates the seismic performances of four different non-ductile RC building frames typical of Haiti and five different techniques to retrofit those. Specifically, the selected RC building frames are of one to three stories and of residential and non-residential functions. The examined retrofit techniques include using RC shear walls, using steel braces, using buckling-restrained braces (BRBs), using prestressed high-strength steel cables, and RC jacketing. To examine the damage of the columns and the beam-to-column joints of the original frame archetypes, their detailed three-dimensional finite element models are initially developed and analyzed via the software LS-DYNA. Subsequently, each frame is retrofitted through three of the above-mentioned techniques. A suite of 11 ground motions is selected and scaled to evaluate the effectiveness of the retrofits by performing time-history analysis on calibrated models on OpenSees. The analysis indicated that these techniques can efficiently retrofit the prototypes of Haitian structures. All the retrofits significantly reduce the interstory drift demand, and the RC jacket significantly increases the moment and shear capacity of the columns.

Mechanical response of elevated bridge piles to adjacent deep excavation

In urban concentrated area, the disturbance caused by construction affects significantly the sustainability of adjacent existing structures. It is essential to capture the mechanical response of existing structures to adjacent deep excavation. The objective of this paper is to investigate the displacement and internal force behavior of elevated bridge piles (BP) subject to influence of deep excavation. A three-dimensional finite element model is established by taking the project of a deep excavation near elevated bridge as an example. The numerically calculated results agree well with the measured data, which verifies the established numerical model. On the basis of this model, the influence of deep excavation on the mechanical characteristics of adjacent piles is captured. The results show that the displacement, bending moment, and shear force of piles are sensitive to the excavation depth. Their magnitudes increase with the increase of excavation depth. When the excavation is completed, the maximum displacements of piles in horizontal direction and vertical direction are 2.3 mm and 10.05 mm, respectively. The maximum bending moment is 1,140.8 kN·m. The maximum and minimum shear forces are 1,206 kN and -2,282 kN, respectively. The piles are mainly under pressure. The maximum pressure is -13,116 kN. The axial force is not sensitive to the depth of excavation. The deformation and internal force of piles exhibit obvious spatial distribution characteristics, and the closer the distance to the middle of the long side of the deep excavation, the greater the value. The research results have a positive effect on the optimization of related engineering structures and the promotion of sustainable development in urban concentrated area.

The biomechanical effects of treating double-segment lumbar degenerative diseases with unilateral fixation through interlaminar fenestration interbody fusion surgery: a three-dimensional finite element study

BackgroundTransforaminal lumbar interbody fusion (TLIF) surgery has become increasingly popular in the surgical treatment of lumbar degenerative diseases. The optimal structure for stable double-segment fixation remains unclear.ObjectiveTo compare the biomechanical changes of unilateral fixation versus bilateral fixation in patients with lumbar degeneration undergoing double-segment TLIF surgery, and to explore the stability and feasibility of unilateral double-segment fixation.MethodsA three-dimensional finite element model of L3-5 was established based on CT data from a recruited young male volunteer, and the model was validated to have reasonable predictive capability. Surgical procedures were simulated by adjusting bony structures to create models of unilateral and bilateral fixation for double-segment TLIF. Under a pure moment of 10 Nm, range of motion (ROM), extension, lateral bending, axial rotation movements, as well as stresses on interbody fusion devices, internal fixation, and endplates were recorded and compared.ResultsUnilateral fixation was fixed on the left side, with both groups performing flexion, extension, left lateral flexion, right lateral flexion, left rotation, and right rotation movements. All reconstructed conditions showed decreased motion from L3 to L5. Unilateral fixation had greater lumbar spine range of motion (ROM) in all directions compared to bilateral fixation. The greatest difference between the two occurred during right lateral flexion at the L3-4 segment, measuring 1.78°. During right lateral flexion at the L4-5 segment, the largest difference was 2.29°. Regarding stress on the fusion devices, unilateral fixation models exhibited higher stresses than bilateral fixation models, but no significant differences in stability were found. Terminal plate stress in unilateral posterior fixation was higher during flexion than in the bilateral model, showing a similar trend in stress changes. No significant difference was seen in internal fixation stress between the two groups during two-segment fusion, with the posterior internal fixation stress in unilateral fixation being 1.7 times higher during flexion and 1.9 times higher during left bending compared to bilateral fixation.ConclusionUnilateral fixation in two-segment transforaminal lumbar interbody fusion (TLIF) surgery can increase stability compared to bilateral fixation, with no significant differences observed between the two models. Unilateral two-segment fixation allows for greater lumbar spine mobility than bilateral fixation, albeit with a slight increase in stress on the posterior fixation and fusion devices under the unilateral fixation mode. This provides some biomechanical evidence for selecting surgical approaches for elderly patients who cannot tolerate long surgeries, suggesting that two-segment unilateral fixation may be advisable.Clinical trial numberNot applicable.

Multiscale Finite Element Modeling of Human Ear for Acoustic Wave Transmission into Cochlea and Hair Cells Fatigue Failure.

Hearing loss is highly related to acoustic injuries and mechanical damage of ear tissues. The mechanical responses of ear tissues are difficult to measure experimentally, especially cochlear hair cells within the organ of Corti (OC) at microscale. Finite element (FE) modeling has become an important tool for simulating acoustic wave transmission and studying cochlear mechanics. This study harnessed multiscale FE models to investigate the mechanical behaviors of ear tissues in response to acoustic wave and developed a fatigue mechanical model to describe the outer hair cells (OHCs) failure. The three-dimensional multiscale FE models consisted a macroscale model of the ear canal, middle ear, and 3-chambered cochlea and a microscale OC model on a representative basilar membrane section, including the hair cells, membranes, and supporting cells. Harmonic Acoustic mode was used in the FE models for simulating various acoustic pressures and frequencies. The cochlear basilar membrane and the cochlear pressure induced by acoustic pressures were derived from the macroscale model and used as inputs for microscale OC model. The OC model identified the stress and strain concentrations in the reticular lamina at the root of stereocilia hair bundles and in the Deiter's cells at the connecting ends with OHCs, indicating the potential mechanical damage sites. OHCs were under cyclic loading and the alternating stress was quantified by the FE model. A fatigue mechanism for OHCs was established based on modeling results and experimental data. This mechanism would be used for predicting fatigue failure and the resulting hearing loss.

Numerical investigation of the railway track lateral resistance with Y-shaped steel sleepers caused by different conditions of the ballast layer

This study employs a three-dimensional finite element model to investigate the effect of ballast material characteristics on railway tracks with Y-shaped steel sleepers. The model's accuracy was validated by comparing its results with those from the Single Tie Push Test (STPT), demonstrating an acceptable error margin of less than 5%. The research assessed the impact of ballast fouling from sand and steel slag, revealing that an increase in steel slag led to a remarkable 125% improvement in lateral resistance. The maximum lateral resistance recorded was at 25% sand contamination, with values of 43.49 kN for Y-foot loading and 38.90 kN for Y-head loading. However, exceeding this percentage resulted in a decline in resistance. The study also identified the contributions of different ballast layer components to lateral resistance: 64% from the crib, 24% from the base, and 12% from the shoulder.

Finite-Element-Based Time-Dependent Service Life Prediction for Carbonated Reinforced Concrete Aqueducts

This study proposes a time-dependent reliability analysis method for aqueduct structures based on concrete carbonation and finite element analysis. The primary goal of this study is to improve the reliability assessment of reinforced concrete aqueducts by incorporating environmental factors such as carbonation over time. First, a three-dimensional finite element model of a reinforced concrete aqueduct is established using the Midas 2022 Civil software, incorporating a time-varying function derived from a predictive model of concrete carbonation depth. Point estimation is then integrated with structural finite element analysis to calculate the first four moments of random variables as functions of concrete carbonation. Additionally, the original performance function is transformed into a normal distribution using dual power transformation and the Jarque–Bera test. The high-order unscented transformation (HUT) is subsequently employed to estimate the first four moments of the transformed performance function, facilitating the calculation of time-varying reliability indices for the carbonated concrete aqueduct. Based on the time-varying reliability index data, a reliability function corresponding to different time points is fitted and applied to service life prediction. The results demonstrate that the proposed method effectively reduces large errors associated with the fourth-moment method in calculating large reliability indices. Furthermore, the comparison with Monte Carlo simulation (MCS) results validates the high efficiency and accuracy of the proposed method, offering a valuable tool for addressing the reliability challenges of aqueducts exposed to carbonation and other environmental factors over time.

THREE-DIMENSIONAL FINITE ELEMENT MODELING OF METAL-BASED NANOCOMPOSITE DRILLING

In this study, a three-dimensional finite element model is developed in Abaqus software to investigate the drilling process of nanocomposites. The research focuses on modeling the chip formation process by incorporating nanoparticles separately and randomly within the metal matrix, providing a more realistic representation. Coulomb's law is utilized to model the friction between the tool and chip, while the Johnson-Cook model is employed to simulate plasticity and failure criteria. The modeling incorporates mechanical and thermal properties of materials as functions dependent on temperature. Dynamic analysis is conducted using Abaqus software to analyze the drilling process. The study reveals that raising the volume fraction of nanotubes from 1% to 5% results in a fivefold increase in required torque. Moreover, the axial force required for drilling increases significantly as the volume fraction of carbon nanotubes rises. For instance, drilling samples with volume fractions of 1%, 2%, and 5% require axial forces of 1,650 N, 1,670 N, and 4,560 N, respectively. These findings underscore the importance of considering nanoparticle volume fraction in optimizing the drilling process of metal-based nanocomposites.

Hemodynamic Evaluation of Intra-Aortic Dual-Balloon Pump Based on Fluid-Structure Interaction.

The intra-aortic balloon pump (IABP) is a widely-used mechanical circulatory support device that enhances hemodynamics in patients with heart conditions. Although the IABP is a common clinical tool, its effectiveness in enhancing outcomes for patients with acute myocardial infarction and cardiogenic shock remains disputed. This study aimed to assess the effectiveness of intra-aortic dual-balloon pump (IADBP) and its impact on aortic hemodynamics compared with an IABP. Three-dimensional finite element models were constructed for the aorta, IABP, and IADBP, followed by numerical simulation using the fluid-structure coupling (FSI) method. Three simulations were conducted: Heart failure patients without assistive devices (Case A), those with IABP (Case B), and those with IADBP (Case C). The study assessed the IADBP's hemodynamic effects by measuring aortic branch blood flow, left ventricular afterload, aortic wall stress, and wall shear stress. IADBP outperformed IABP in enhancing blood flow to the coronary arteries, upper limbs, and brain vessels (left and right coronary arteries: 0.88 vs. 1.27, 1.27 vs. 1.99 mL/beat; brachiocephalic artery, left common carotid artery, and left subclavian artery: 6.08 vs. 12.39, 2.48 vs. 4.97, 2.31 vs. 5.08 mL/beat). IADBP also demonstrated superior performance in counterpulsation pressure and left ventricular ejection (counterpulsation phase: 97.41 mmHg vs. 110.03 mmHg; ventricular unloading phase: 72.21 mmHg vs. 66.46 mmHg). The use of IADBP elevates stress on the aortic wall and wall shear stress, potentially affecting vascular health. IADBP effectively addresses upper limb and cerebral hypoperfusion issues associated with IABP, demonstrating superior performance in enhancing counterpulsation pressure and left ventricular ejection. Despite potential vascular biomechanical effects, IADBP provide a promising clinical treatment option. Further studies are needed to refine IADBP 's design and evaluate its long-term clinical efficacy.

A finite element analysis to assess tibial bone fracture in malleolar regions following total ankle replacement: Influences of implant designs and implant-bone interfacial conditions.

Tibial bone fractures in the malleolar regions are a major concern during the early postoperative period of total ankle replacement (TAR), affecting patient outcomes such as stability and recovery. Design, placement, and anatomic misalignment of implant components can contribute to malleolar fractures. The aim of this study is to understand the influence of implant design features, including keel, peg, stem, and bar type design, and bone-implant interfacial conditions on malleolar fracture following TAR. Three-dimensional finite element (FE) models were generated for the intact and implanted tibia bone using computer tomography (CT) scan data. In the present study, both bonded (fully osseointegration) and debonded (non-osseointegration) implant-bone interface conditions were considered. The proximal part of the tibia was fixed. Finite element models of the intact and implanted tibia were solved for three distinct loading situations that correspond to three ankle positions throughout the gait cycle (GC). The influences of implant design and implant-bone interface conditions on malleolar fracture were examined by evaluating stress distribution in tibia bone post-implantation. Finite element (FE) analysis revealed that for the medial region, the tibia bone stress elevated to 10 MPa for the medial keel type design, indicating a possible fracture along the medial region. The risk of a medial malleolar fracture is highest for the medial keel type implant design compared to other designs. The bars, central keel, and stem type TAR implant designs also elevate stress on both the medial and lateral regions of the tibia bone. In the case of fully osseointegrated implant-bone interface conditions, the stress is slightly higher than in the case of non-osseointegrated implant-bone interfacial conditions. The study highlights the potential influence of specific implant designs on malleolar fracture. The current findings are crucial for designing new implants to mitigate tibial bone fracture risks and improve TAR outcomes.